Pulsed droplet deposition apparatus of kind referred to above is known in the art in many different forms and configurations:
EP-A-0 278 590 discloses arrangements comprising a plurality of droplet liquid channels and nozzles for ejection of droplets of liquid, wherein ejection of droplets is achieved by displacement of channel-separating walls in response to actuating signals. This document outlines several alternative methods of displacing the channel walls, including the use of piezoelectric material in shear mode, in direct mode and in bimorph configuration.
U.S. Pat. No. 5,277,813 discloses another type of pulsed droplet deposition apparatus of kind referred to above which utilises piezoelectric material subject to an electric field in the depthwise direction and displaceable in shear mode relative to the channel.
EP-A-0 611 654 discloses pulsed droplet deposition apparatus of the kind referred to above and which employs electrostatic attraction forces to displace the channel walls.
In such known apparatus, it is desirable for the active, ink ejecting channels at either end of an array of adjacent active, ink ejecting channels to operate in the same fashion as the other channels in the array, namely for both walls either side of a channel to displace (generally, but not always, in opposite senses) when drawing in or ejecting ink. To this end it has been necessary for the array of active channels to bounded at each side by one or more "guard" channels which, whilst they do not eject ink, nevertheless permit the outermost wall of each outermost active channel of the array to be displaced.
Furthermore, it is known in the art that pulsed droplet deposition apparatus of the kind referred to above should be used for the simultaneous printing of more than one colour: WO95/07185 discloses the construction of an ink jet printer having a number of sub-heads each supplied with a different coloured ink via a separate ink manifold. It is disclosed that the sub-heads may be mounted parallel to one another and offset--either across or in the direction of motion of the printhead--or may be mounted with the respective array directions collinear. The document goes on to state that the sub-heads may be separate components or may be formed in a single coextensive ceramic wafer.
It is an objective of the present invention to simplify both the construction and the manufacturing process of apparatus comprising a plurality of sub heads of the kind referred to above, each sub head being supplied from a separate manifold chamber.